PETROLOGY OF THE WESTERN CARPATHIANS CRETACEOUS PRIMITIVE ALKALINE VOLCANICS

Abstract: In several Mesozoic tectonic units (Silesian, Tatric and Fatric ones) of the Western Carpathians, different alkaline effusive and rarely also intrusive rocks of the Cretaceous age (approx. 100 Ma) are known. Olivines, clinopyroxenes and less frequently also amphiboles form phenocrysts, and glomerophyric accumulations of them occur in places. Fine-grained devitrified matrix (up to 40 vol. %) is another constant rock component. The nature of Cpx phenocrysts documents a rapid ascent of the melt which was contaminated by the resorption (mostly of carbonates) of xenoliths. The variable composition of these rocks is mainly a result of fractional crystallization and xenolith assimilation. According to their chemical composition these rocks correspond to alkaline basalts/basanites, locally even picrites. The presence of primitive alkaline volcanics is a consequence of extending volcanic activity in their respective units.